Shit just got real in Joss Whedon's Avengers shoot. Some new set photos and videos reveal Captain America locked in battle with a mysterious threat... and there are some pretty good clues as to what that threat is. Spoilers below...

So the latest set photos from Cleveland give us our best look so far at the modern version of Captain America's suit — which is sort of a mixed bag. On one side, there's no more chinstrap and less bulky stuff attached to the torso. On the other hand, it's a lot more brightly colored and more overtly "comic-booky" than the somewhat toned down version in Cap's origin story.

And then there are photos of an action scene in which Cap fights some invaders, who are wearing motion-capture suits. Are they aliens? People in mecha suits? We don't know yet. But they're holding what look like alien super-weapons: